528 EXPLORERS' JOURNEYS IN HIGH TIBET.
have been almost a complete ring in comparatively recent historical times, when it was continuous with the Devil's Lake across that narrow isthmus now so consolidated that we cantered over it on the way on our visit to Samding. Its two ends are only separated by the Tag ridge. The people say, and indeed there is ample evidence, that the larger lake is drying up and receding. As we passed along its shore we could see the old tracks on the hill-side 20 to 3o feet above the present road, and in the side valleys were well-marked shallow terraces, for I oo feet or more, marking evidently former levels of the beach. Its water undoubtedly extended in former times up the side valley, down which we came to near the Kharo Pass, as the shelving shingly plain, spotted with white saline incrustation, forming the bed of that valley, was clearly continuous with the floor of the lake. The level of the water nowadays fluctuates within narrow limits from year to year, and with the season according to variations in the local snow and rainfall. The desiccation of this lake is doubtless due in part to the increased evaporation consequent on the disappearance of its glaciers and glacial feeders permitting the air to become warmer, whilst the rising of the Himalayas, which has continued up to recent times, must have cut off a considerable amount of its former rain supply. The water of the lake tasted slightly saline, as was to be expected in a lake which had no outlet, and which was fed by rain and snow from the hillsides, dissolving portions of the lime and other rocks, and an evaporation leaving the salt behind ; but although slightly brackish it was quite drinkable and made good tea.»*
With regard to the Dum-tso (the »Devil's Lake)) Waddell says: »It is on practically the same level as the Yamdok, not more than I or 2 feet higher, and is merely a portion of the latter which has become detached and isolated by the drying up of the waters of the great lake.»
I cannot here let slip the opportunity of pointing out the extremely remarkable geographical homology that exists between the Jamdok-tso and the Naktsongtso, which I mapped and in part sounded. Both these lakes have been formed by nature on precisely the same model, and it must be pronounced a very singular thing that a lake which is intrinsically abnormal in shape should be paralleled by another at no great distance away. The resemblance between the two lakes is at least as great as that between the islands of Celebes and Dschilolo (Jilolo or Halmahera) in the East Indian Archipelago. The photographs of the Jamdok-tso which were taken by the members of the English mission might equally well pass for views of the Naktsong-tso. The most important differences between the two lakes lie partly in their size, the Jamdok-tso being a good deal the larger, and partly in the fact that the rocky island of the latter is connected with the mainland on the west by three narrow strips of ground and consequently is in reality a peninsula, whereas the island of the Naktsong-tso is united with the mainland by merely a narrow alluvial isthmus of a wholly secondary character, it too being on the west. In both alike the greatest expanse of water lies east of the island ; in both alike the shores are fringed by smaller islands, headlands, and bays; and in both alike there exists a tiny isolated
* Lhasa and its Mysteries, with a Record of the Expedition of 1903-1904, by L. Austin Waddell, p. 298.
** Op. cit, p. 297.
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